1. Field of Invention
The present invention relates, in general, to a photographic printing method and a printer for producing three-dimensional (3D) pictures on lenticular print material.
2. Prior Art
In lenticular 3D photography, the basic process involves taking a plurality of two-dimensional (2D) images of a scene from a number of horizontally-spaced vantage points, and exposing the 2D images on lenticular print material through one or more projection lenses at different projection angles. It is well-known that lenticular print material is made of a lenticular screen coated with or attached to a photosensitive emulsion, and a lenticular screen is a transparent sheet embossed with an array of contiguous semi-cylindrical lenses, or lenticules. When an array of 2D images are exposed through the lenticular screen, these 2D images are optically compressed to become line-form images. It should be kept in mind that a 3D picture is composed of 2D images of slightly different views of a scene, therefore, these 2D images must be accurately aligned with each other in reference to a point in the scene. This reference point is known as the "key subject" in 3D photography and the alignment process is usually referred to as "key subject alignment".
U.S. Pat. No. 5,028,950 (Fritsch) discloses a dual-stage 3D printer in which a single projection lens is used to expose at different projection angles a set of 2D images of a scene recorded on film. U.S Pat. No. 4,903,069 (Lam) also discloses a 3D printer which uses a single lens to expose a set of 2D images recorded on film onto lenticular print material. In these disclosed methods, in order that the photosensitive emulsion underlying the lenticules be filled with compressed line-form images, a scanning mechanism is required to move the projection lens, the print material, relative to the negative images, to different positions to change the projection angles. This requirement demands a mechanical design with high levels of sophistication. Moreover, in both disclosed methods, a very complex scheme must be used to perform key subject alignment.
U.S. Pat. No. 4,111,236 (Lo) discloses a method for simultaneously printing three 3D pictures through a common projection lens. With this disclosed method, each piece of print material must be exposed three times at three different projection angles from the same set of 2D images recorded on film. This method does not require moving the projection lens relative to the 2D images, but the print material must still be moved to different locations to change the projection angles. Furthermore, with the Lo's method, the three 2D images recorded on film must be physically separated so that the key subject in each image can be properly aligned prior to printing. Because this procedure is very tedious and time-consuming, it is useful only for printing multiple copies of 3D pictures in large quantities. This method is impractical for printing consumer 3D pictures in single copies or in small number of copies.
In all the above-mentioned methods, only a relatively small number of 2D images can be used to compose a 3D picture. Such a 3D picture usually appears "jumpy", especially in the far background or near foreground areas.
U.S. Pat. Nos. 4,166,684 (Law), 4,125,849 (Law) and 4,107,712 (Law) disclose a camera for taking a 3D picture from a real scene wherein the aperture of the camera is movable transversely across the taking lens to change the vantage points, and the lenticular screen is moved in relative to the photographic emulsion. With this method, the lenticular screen and the photosensitive emulsion must be separable. Thus, the method disclosed by Law cannot use lenticular print material precoated with photosensitive emulsion. Moreover, after chemical processing, the photosensitive emulsion must be laminated to a viewing screen to become a 3D picture.
It is advantageous to provide a printer of simple design, wherein the movement of projection lens and the print material in relation to the 2D images is not required. Moreover, it is desirable to provide a printer capable of making 3D pictures of high quality on precoated print material.